Ink mist prevention system using pointed electrode members



June 2, 1970 B. H. VLIER 3,515,054

INK MIST PREVENTION SYSTEM USING POINTED ELECTRODE MEMBERS Filed Oct. 4, 19s?- 3 Sheets-Sheet 1 INK MIST PREVENTION SYSTEM usme POINTED ELECTRODE MEMBERS Filed 001;. 4, 1967 B. H. VLIER June 2, 1970 3 Sheets-Sheet 2 June 2, 1970 H. VLIER 3,515,064

INK MIST PREVENTION SYSTEM USING POINTED ELECTRODE MEMBERS Filed Oct. 4, 1967 3 Sheets-Sheet 3 United States Patent Int. Cl. B411? 31/00 US. Cl. 101349 Claims ABSTRACT OF THE DISCLOSURE A system for use on printing machines to prevent the formation of an ink mist having a support member with nail-like members supported on the member uniformly spaced along its length and electrically connected to gether. The support member is supported at its ends in sockets and positioned parallel to a roller couple nip with the nails aimed into the nip. A high potential difference is created between the nails and the rollers so that an electrostatic field emanates from the points of the nails and onto the rollers to prevent the formation of any ink mist particles in their incipiency.

Background of the invention This invention relates to an ink mist eliminator and more particularly to a system for preventing the formation of an ink mist in high speed printing presses and the like and is a continuation-in-part of my copending application Ser. No. 464,440, filed June 16, 1965, now abandoned, for Ink Mist Eliminator.

As the speed of printing presses has been increased, the problem of ink misting has become more and more important. It is generally believed that the ink mist is formed as a result of the rupturing of filaments or stringers of ink formed at the exit nip of a roller couple. There are many factors which influence the amount of mist created, the predominant factors being the speed of the rollers and the various properties of the ink such as its viscosity.

The dangers to health, contamination to equipment and finished product, cost of wasting and cleaning up ink mist deposits, as well as other factors, have prompted the development of various systems for controlling the mist. These proposals range from providing the pressroom with a number of high powered fans for drawing the ink laden air through air filters to an exhaust system to providing fans to carry the ink laden air to an electrostatic precipitating unit where the ink is removed. Neither of these methods has proven to be satisfactory in the long run because of the expense and inconvenience in replacing the filters or cleaning the precipitator. In addition the efiiciency of the systems has not been as high as would be desirable.

More recently, it has been proposed that the ink mist could be suppressed by establishing an electric field between the roller couple and a wire positioned a short distance from the exit nip of the roller couple, the potential difference between the wire and the roller couple being great enough to establish a corona discharge around the wire. The corona discharge results in ionization in the air in the vicinity of the wire and the ionic charge is transferred from the air to the ink mist particles. The charged ink mist particles are then forced back onto the rollers as a result of the electrical field acting on them. While this system has the advantage of forcing the ink back on the rollers and thus eliminating the problem of removing it from something else such as a filter or a precipitator, it

Patented June 2, 1970 has been found in practice that the efiiciency of the system is not as high as might be desired because a significant number of the ink particles manage to avoid being charged until they have travelled past the wire and they are then forced by the electric field to the nearest ground which at this point is often not the rollers. Also many of the ink mist particles escape the ions and tend to collect on and coat the thin wire electrode. After sufiicient passage of time the weight of the ink on the wire tends to cause the wire to sag thereby decreasing the etficiency of the system because the corona around the wire would no longer be located at the proper distance from the roller couple. Because this type of electrode lacks rigidity it also has the disadvantage of being susceptible of breaking. Finally, this type of electrode has the inherent disadvantage of arcing.

It has also been proposed to position a manifold having a thin slit therein adjacent the nip of a roller couple and supply a gas under pressure to the manifold so as to direct a stream or sheet of air into the nip. By providing this sheet with a sufficient velocity, it has been found that misting can be greatly reduced. A system incorporating such a system, however, is impractical in a modern pressroom. First, the physical size and mechanical complexities of the system make it undesirable and awkward. More importantly, the velocity of air leaving the manifold is from one to three times the printing machine web speed and the quantity of air in the stream directed at the nip is excess1ve.

Since it appears that the formation of any ink mist will inevitably result in problems in containing it, it is a primary object of this invention to prevent the formation of any ink mist in the first instance. This object has been accomplished by establishing an electric field between the roller couple and a specially designed electrode. The electrode design is such that an ionized air stream or electric wind is directed at the exit nip of the roller couple. This ionized air movement or wind has only a small fraction of the linear velocity or quantity of that required by the air manifold system mentioned above, but still forces back into the film any incipient filaments or stringers formed as the ink film splits. The ink is thus maintained in a single body and no filaments are formed which could rupture to form the ink mist.

Another object of this invention is to provide an improved electrostatic ink mist prevention system having an electrode which is of a rigid construction thereby eliminating the possibility of the electrode losing its effectiveness due to a change of position with respect to the rollers.

A further object of this invention is to provide a system for preventing the formation of the ink mist which does not produce sparking or arcing.

Other objects, advantages and features of the present invention will become more apparent from the following detailed description in connection with the accompanying drawings.

Brief description of the drawings In the drawings:

FIG. 1 is a front elevational view of the arrangement of he present invention mounted on a unit of a printing press;

FIG. 2 is a section taken along line 22 of FIG. 1 and showing the ink train of a typical printing press unit;

FIG. 3 is an enlarged front view of the electrode used in the present invention;

FIG. 4 is a side view of one end of the electrode shown in FIG. 3;

FIG. 4A is an enlarged section taken along lines 4A4A of FIG. 4;

FIG. is a side view of the other end of the electrode shown in FIG. 3;

FIG. 6 is a front view of the socket supporting one end of the electrode on the press unit;

FIG. 7 is a section of the socket supporting the other end of the electrode;

FIG. 8 is a block and schematic diagram of the power supply used to energize the present system;

FIGS. 9A, 9B and 9C illustrate the manner in which an ink mist is believed to be formed at the exit nip of a roller couple; and

FIG. 10 is an enlarged sectional detail of the exit nip of a roller couple provided with the present invention.

Description of the preferred embodiment of this invention FIG. 1 shows the electrodes 23 of the present invention mounted in position between frames 10, 11 of the printing machine. Mounted on the frames 10, 11 are brackets 12. Supported between brackets 12 are mounting plates 13, 14. These plates must be of an insulated material. Past experience has indicated that this material should preferably be Bakelite, however, any suitable insulating material will do. The plates 13, 14 are supported from the side frames 10, 11 by insulating studs 15 bolted by means of bolt 18 to the bracket 12. The electrodes 23 are supported in sockets 19, 20 which are mounted on the mounting plates 13, 14 respectively by means of bolts 21, 22 respectively.

FIG. 2 shows a portion of a typical ink motion. Distributing cylinders 16 and rollers 17 are mounted between the frames 10, 11 by means of their respective steel shafts 35, 36. The ink which is ultimately to be distributed to a printing plate cylinder 37 for deposition onto printed matter is transferred from One distributing drum to another by means of rollers 17 so as to insure uniform distribution of the ink. The direction of rotation of the various rollers is indicated by the arrows in FIG. 2. The electrodes 23 are located at various points in the ink train. These are positioned adjacent to each of the exit nips of the various roller couples where ink misting is most likely to occur, that is, at the nips of the various roller couples 16, 17.

Turning now to FIGS. 9A, 9B and 90 the fashion in which ink mist is believed to be formed is shown. When the two rollers 38 and 39 rotate at high speeds, and one or both of them has an ink film formed thereon, there is formed at the nip 40 an area where ink filaments or stringers 42 are formed as a result of the viscosity of the ink opposing the motion of the rollers in splitting the ink film. In FIG. 9B, the leading filament 42 has been elongated by further travel of the rollers 38 and 39 to the point where its viscosity is no longer sufficient to hold it together and it breaks. The rupturing of this filament results in the formation of a large number of minute particles 44 which forms the ink mist as shown in FIG. 9C. The remainder of the filament or stringer is merged back into the ink films on the rollers.

The details of the electrode of the present invention are shown in FIGS. 3, 4 and 5. The electrode comprises an elongated tube 23 acting as a support carrying a plurality of nails or nail-like members 24 electrically joined together and driven through a plurality of holes uniformly spaced along the length of the tube and on opposite walls of the tube. The nails need not be driven through the tube but can be supported therefrom in other suitable ways. The tube may be made of a conductive metal, such as aluminum, in which case no other connection between the nails is necessary as the tube itself will serve as the electrical connection between the nails. When however, the support is of an insulated material connection between the nails may be established by means of a wire or other conductor twisted around the nails or otherwise connected thereto. The holes 25 have a diameter somewhat smaller than the diameter of the nails so that the nails are securely held in the tube. The nails are dis- 4 posed perpendicular to the longitudinal axis of the tube and aligned in a comb-like manner.

At one end of the tubular support there is a pin 29 secured in the tube and disposed perpendicularly to the axis of the nails and the axis of the tube. At the other end there is a plunger 26, also made of conductive metal, slidably inserted in the tube with a portion thereof protruding. The plunger is cylindrical in shape with one end thereof closed 01f and rounded. Within the plunger there is a helical spring 27 abutting at one end thereof against. the inner surface of the closed end of the plunger 26. The other end of the spring abuts against the nail-like member 24 passing through the first hole of the tube. The plunger 26 also has a slot 28- extending partially along its length on opposite walls for allowing the nails 24 to pass through the plunger without interfering with its sliding movement.

The electrode, comprising the support member and the nails carried thereby, is mounted in sockets 19 and 20 which are secured to the insulated mounting plates 13 and 14 respectively as shown in FIGS. 6 and 7. Socket 19 supports that end of the electrode which is fitted with pin 29. The pin fits into a slot in the socket so as to prevent any wobble or rotation of the electrode. Socket 20 supports the other end of the electrode and is designed to receive the spring loaded plunger 26. As seen in FIG. 6 the plunger is urged against an exposed tinned wire 30 by the spring so as to make a secure electrical connection. The wire 30 is carried in a conduit 31 to a connection block 32 as shown in FIG. 2. Electrical connection is then made with connector 34 which is connected to a high voltage power supply 33, which is shown in more detail in FIG. 8. If the support member is of a construction other than that shown or of a nonconductive material other suitable means for connecting the nails 24 to the power supply would be provided.

The electrode is mounted by first inserting the plunger end into socket 20, depressing the spring 27 by pushing the electrode into the socket 220 then inserting the pin, at the other end of the electrode, into the slot on socket 19, then releasing the electrode and allowing the spring 27 to exert a longitudinal force along the electrode so as to keep both ends secured within their respective sockets.

In a preferred construction of the electrode the tube 23 has an outside diameter of approximately three-quarters of an inch and a wall thickness of approximately three thirty-seconds of an inch. The nails protrude beyond the surface of the tube approximately three-quarters of an inch and are spaced from one another along the length of the tube approximately three-quarters of an inch apart. The deflection of the tube is one thirty-second of an inch or less, which is within the permissible variation in placement of the electrode nail tips 24' with relation to the ink motion rollers.

The ink drums 16 and rollers 17 are mechanically connected to the frame of the machine and consequently are electrically grounded. The electrode 23 is connected to the power supply 33 and a negative DC potential of approximately 12,000 volts is maintained thereon. As a result of the construction of the electrode and the high potential difference created between the electrode and the rollers a steady flow of ions is emitted from the space at the tips of the nails 24 and directed into the nip of the various roller couples and onto the rollers 16, 17, thereby creating a steady directional electric wind and flow of ionized air.

As seen in FIG. 10 the electric field established between the pointed members 24 and the rollers 16, 17 creates lines of flow 54 emanating from the points 24' of the members 24 and onto the rollers 16, 17. Because of the pointed nature of the members 24, the resultant ion flow is of high intensity and is directional. The pointed members 24 are spaced along the length 'of the support tube 23 as described above such that their fringe fields overlap at the nip of the roller couple to form a field of uniform intensity along the entire length of the roller couple nip, ionization occurring primarily at the points or sharp edges of the nails 24. The nail tips 24, as shown in FIG. 4A, are of a pyramidal configuration. The point of the nail tip is blunt, and two edges of it 67 and 68 are rounded and smooth due to the process of manufacture. The other two edges 65 and 66 have a rough jagged surface forming the fine points about which the optimum ionization takes place with 12,000 volts maintained on the nails and with the tips 24' spaced approximately one inch from the grounded surfaces of the rollers.

The effect of this dynamic directional field is shown in FIG. 10. As shown in this figure the roller 17 has a rubber covering. The presence or absence of such a covering does not, however, materially affect the operation of the system of the present invention. The position in which the pointed member 24 should be placed will de pend on the position of the metal cylinder supporting the rubber covering. Ideally, the point 24' of the nail 24 should be placed equidistant between the grounded conducting surfaces of each roller of the couple. For example, if the rubber covering is /2 inch thick the point 24' of the pointed member 24 may be placed 1 inch from the surface of the steel drum 16 and inch from the surface of the rubber covered roller 17, thereby being 1 inch from the steel shaft 36 of the rubber covered roller 17. As was the case in FIG. 9, the rollers 16 and 17 turning at a high angular velocity would normally cause stringers or filaments to be formed at the nip. If, however, electric force field is established between the rollers 16, 17 and the pointed members 24 as a result of a potential difference being applied between them, and if the potential difference is sufficient to cause an electron flow from the points 24 of the nails 24, and consequent ionization of the air, surrounding them, an electric wind of substantial velocity will be formed which will follow generally the lines of force of the electrical field. It is believed that this wind is formed as the result of the flow of negatively charged air molecules away from the nails 2-4 and towards the other side of the field i.e., the nip 40. The air molecules become negatively charged by their picking up an excess electron which is freed as a result of ionization of the air by the discharge of the point 24' of the pointed member 24.

By establishing a high enough potential difference between the nails and the rollers, the resultant electric wind can be made of sufficient velocity to offset the forces exerted by the viscosity of the ink and thus in effect drive any incipient filament back into the main body of the ink and thus prevent the formation of any filament that could be elongated sufficiently to rupture. To look at the operation of the wind in another manner, it could be considered as acting as a wedge which positively and cleanly separates the ink body 55 into two separate ink films 56 and 57. This separation into two films is thus not solely dependent upon the rotation of the rollers and the physical properties of the ink but is rather accomplished by an external agency which by cleaving the ink body as it emerges from the nip prevents the physical nature of the ink from trying to draw some portions of it in two directions at once.

FIG. 8 shows in block diagrammatic and schematic form the high voltage power supply which has been found to be acceptable for use in the present system. The output of this power supply is to be connected through jack 3-4 to the connection block 32 for distributing 12,000 volts of negative DC potential to each of the electrodes. This high potential is obtained through a typical voltage doubling circuit. This circuit comprises a magnetic core transformer 48 with line voltage impressed on its primary and a secondary voltage of approximately 6,000 volts, a pair of diodes 59 and '60 rated at 19,000 volts in bridge connection with a pair of condensers 61 and 62 each having a value of .03 microfarad at 10,000 volts. Shunted across each condenser is a resistor 63 and 64 each having a value of 15 megohms, 4 watts for bleeding off any residual voltage stored in the condensers when the system is turned off. The high voltage output is tapped off from a point between diode 59 and condenser 61. This circuit is connected between line current L1 and L2 and in series with a set of protective fuses 43, a first set of normally open relay contacts 46, a circuit breaker 53, a set of safety switches 58 which are closed when the protective guards are in place on the printing machine, and a second set of relay contacts 47. A red indicating lamp 50 is connected in parallel with this circuit for indicating that the high voltage is on.

The circuit breaker 53 can be of either the instantaneous type or of the time delay type. If an arc between the electrode and the rollers were to occur, an excess of current would be drawn through the voltage doubling circuit and would cause the circuit breaker 53 to trip and turn off the high voltage. Connected to the circuit breaker and in parallel with the voltage doubling circuit and the red lamp is a green lamp 51 to indicate Whether or not the circuit breaker has tripped. If the time delay type breaker is used only an arc of finite duration will trip it. Experience has indicated, however, that no arcing occurs in the normal operation of this system and it is therefore preferred to use the instantaneous type breaker.

Connected to the voltage doubling circuit at a point between diode 60 and condenser 62 is a circuit 49 for detecting the condition of the electrodes. If the nails 24 become dirty or contaminated with ink deposits the current in this detector circuit will decrease and the lamp 52 will go on to indicate that the electrodes require cleaning.

The interlock switch 44 is preferably operated by centrifugal force and is located on the press drive of the printing press unit. This switch is set to close when the printing press unit is operating at approximately 15,000 papers per hour. When the press is up to this speed relay 45 will become energized closing relay contacts 46 and 47 and the circuit through the voltage doubling circuit and electrode condition detector circuit will be established to supply the electrodes with the desired high voltage potential.

From the foregoing description, it can be seen that a system has been provided for preventing the formation of ink mist at the exit nip of the various roller couples in a printing press. This is achieved by creating an electric wind which acts to prevent the formation of any filaments or stringers at the nip. Since it is the rupturing of these filaments that is the cause of ink misting, this action effectively eliminates the creating of the mist. An electric wind of suitable direction and velocity is caused to be created by the use of a unique electrode structure which creates a very directional dynamic electric field between itself and the rollers. In the event of a paper wrap, the electrode is not drawn into the rollers but cleanly perforates and shreds the paper with the result that no damage is done to the system.

What is claimed is:

1. A system for preventing the formation of an ink mist at the exit nip of a roller couple of a printing press when ink is transferred from one to the other of the rollers comprising, an electrode positioned adjacent to and along the length of said nip, said electrode comprising an aluminum electrically conductive supporting tube having a plurality of electrically conductive nail-like pointed members disposed through said tube extending toward said nip at substantially right angels to the length thereof, each of the points of the said nail-like members being a four sided pyramid with sharp edges for ionizing the adjacent medium, electrical power supply means for establishing an electric field between said rollers and the ends of said pointed members of suflicient potential to cause the medium surrounding said members adjacent said sharp edges to ionize, said members being disposed along the entire length of said nip so that the fields of adjoining members overlap to establish a relatively uniform field strength at the nip olong the entire length thereof, said nail-like members being maintained at a negative potential relative to said rollers and said field causing the movement of ionized air into said nip at a velocity sufficient to prevent the formation of ink filaments at said nip.

2. The system of claim 1 wherein said power supply comprises a voltage doubling circuit having a high voltage output for creating said potential difference sufiicient to ionize the air surrounding said pointed members, a circuit for detecting the condition of said electrode connected to said voltage doubling circuit, means for indicating the condition of said electrode responsive to a decrease in current in said electrode condition detecting circuit and connected to said electrode condition detecting circuit and means for immediately turning off the high voltage when any are occurs between the electrodes and any grounded surface.

3. The system of claim 2 wherein said potential difference is approximately 12,000 volts.

4. The system of claim 1 wherein said support member is an aluminum tube having an outside diameter of approximately three-quarters of an inch and a wall thickness of approximately three thirty-seconds of an inch.

5. The system of claim 4 wherein said nail-like members are disposed in said aluminum tube in a comb-like manner.

6. The system of claim 5 wherein the ends of the said nail-like members are positioned an equal distance from the grounded metalic surfaces of each of said rollers.

7. The system of claim 6 wherein said nail-like members are space approximately one inch from the grounded metalic surface of each of said rollers and three-quarters of an inch a part.

8. The system of claim 7 wherein the tips of said pointed members have a pyramidal shape with the point thereof blunt, having two edges of the pyramid smooth and the other two edges jagged forming fine points at which ionization takes place.

9. A system for preventing the formation of an ink mist at the exit nip of a roller couple of a printing press when ink is transferred from one to the other of the rollers comprising an electrode mounted between the frames of the printing press positioned adjacent to and along the length of said nip, a socket mounted on the inside surface of each of the frames of the press for supporting therebetWeen said electrode, said electrode comprising an aluminum tube having a plurality of relatively even spaced, electrically conductive, nail-like members disposed in said aluminum tube in a comb-like manner and extending toward said nip at substantially right angles to the length thereof, one end of said aluminum tube having a pin secured therein being disposed perpendicular to the longitudinal axis of of said tube and perpendicultr to the axes of said nail like members so that said end may be fitted into the socket on one of said frames in such a manner that rotation of the tube in said sockets is prevented thereby maintaining proper orientation of said nail-like members toward said nip, the other end of said aluminum tube electrode having a spring loaded plunger mounted therein for axial movement so that said other end of said electrode may be easily and rapidly inserted in the socket on the other of said side frames, and so that said spring loaded plunger biases said electrode in an axial direction so as to secure said electrode within its respective sockets, an electrical power supply connected to said rollers and said electrode for establishing a potential difference between the ends of said members and said rollers to maintain said members at a negative potential relative to said rollers and sufficient to ionize the air surrounding said members, said nail-like members being disposed along the entire length of said nip their tips being positioned an equal distance from the grounded metalic surfaces of each of said rollers so that the fields originating at adjoining members overlap at said rollers to establish an electric field of relatively uniform strength along the entire length of said nip, said field causing the movement of ionized air into said nip at a velocity sufficient to prevent the formation of ink mist.

10. The ink mist prevention system according to claim 9 wherein the socket mounted on the inside surface of one of said frames is electrically insulated therefrom and has a slot for receiving that end of the electrode fitted with said pin and wherein said other socket is also electrically insulated from its frame and said other socket is provided with electrical conductive means for connecting said electrode to said power supply.

References Cited UNITED STATES PATENTS 2,097,233 10/1937 Meston.

2,195,431 4/1940 Shively et al. al52 X 2,753,796 7/1956 Wood et a1 10l147 2,842,053 7/1958 De Marchi 10l349 3,011,435 12/1961 Jones et al. 101350 3,174,748 3/1965 Roberts et al.

3,295,441 1/1967 Garnier 10l-349 3,323,794 6/1967 Brandt 22694 X OTHER REFERENCES Mendenhall et al.: College Physics, Heath and Company, Boston, 1944, pp. 362, 363.

Spinney: A Textbook of Physics, M acMillan, New York, 1937, pp. 332-336.

ROBERT E. PULFREY, Primary Examiner E. H. EICKHOLT, Assistant Examiner U.S. Cl. X.R. 1014l6 

